[Tiersin]

Ok, i understand theres probably a million posts on this topic, but i really dont have time to go through and read them all. I am thinking about doing a head swap. I know i will need stuff like a OBD converson harness, and of course a new head. What is the best head? what are the differences between a Z6 and a Y8? Where could i find a total "Ho To" on the swap? What all would i need to get in order to do this swap? And if you knew a ballpark price, that would be great. Sorry for making a redundant post, i will keep looking around though. Thank you.

Oh, one more thing, what exactly is a "Mini Me"? I've herd it everywhere, but i dont know what it is.

 

[OBD1 Kenobi]

Oh, one more thing, what exactly is a "Mini Me"? I've herd it everywhere, but i dont know what it is.

A mini me is a nickname for the Z6 or Y8 head swap.

 

[Stavros]

from what ive read on the subject, the only heads you can swap onto your D16 block are the Z6 or the Y8. the Y8 is the easiest to do because you dont need to modify your distributor to mount up to it. the Z6 needs some tinkering to do it properly.

these heads are both (?) SOHC Vtec heads, and will give you a bit more kick than the standard A6 head. Either one will be a "mini-me" swap. the problem with mounting either one of those heads is higher compression ratio (which means early explosions in your combustion chamber, BAD for your car!!! think... piston going up in cylinder, but combustion happens to early... piston still has to go up... what will break first, piston? conn rod? head gasket?)

if you dont swap your ECU with the head (and mess with the wiring) then you will have to rig up a Vtec control switch, which still works, but it wont be as effective, since the ECU vtec control also changes the fuel curve if im not mistaken.

youll have to look around for prices on your own, dont expect to pick up your head for really cheap unless there is something wrong with it. and there are How-To articles around, here are some that i got when i asked the same question:

http://crx.honda-perf.org/articles/moreminime/moreminime.html

here is the thread where i asked this first:

http://crxcommunity.com/viewtopic.php?t=535&highlight=

not to try and flame or anything, but try using the search function. if you narrow your search down to specifics (mini-me, y8 swap or z6 swap) you will probably get the results you are looking for.

hope this helps

 

[Kain]

Either one will be a "mini-me" swap. the problem with mounting either one of those heads is higher compression ratio (which means early explosions in your combustion chamber, BAD for your car!!! think... piston going up in cylinder, but combustion happens to early... piston still has to go up... what will break first, piston? conn rod? head gasket?)

last i knew the combustion in the chamber came as a result of a spark. the timing of this spark has nothing to do with CR but can be advanced or retarded as needed...

 

[Tiersin]

No, hes right on this, the AF mixture can ignite itself under lots of heat and pressure. This is how Diesel engines work...which is good for them, but not good for Rex's

 

[ollie]

No, hes right on this, the AF mixture can ignite itself under lots of heat and pressure. This is how Diesel engines work...which is good for them, but not good for Rex's

Yikes let me clear this bit of misinformation up if I may.
Using the analogy for diesels does not apply here because diesels run an avg of 17:1.
Adding a Z6 head to an A6 block yields a 9.9:1
Adding a Y8 head to an A6 block yields a 10.3:1
Although compressing fuel under high CR is true that doesnt apply here.
Also a higher CR doesnt mean "a earlier explosion".
The cam and the ECU control the timing,not the CR.
Although it is true that you have to retard the timing slightly on higher CR motors,With the CR we are discussing pertaining to a mini-me's thats not the case.
Also it should be noted that the P28 is the ECU of choice for mini-me swaps.
Not to bust on anyone,but I hope that helps and If you need any help PM me I have been there,done that.

 

[dohcrxl]

these heads are both (?) SOHC Vtec heads, and will give you a bit more kick than the standard A6 head. Either one will be a "mini-me" swap. the problem with mounting either one of those heads is higher compression ratio (which means early explosions in your combustion chamber, BAD for your car!!!

ollie caught it but let me further clarify the point - higher compression than the stock 9.1 doesn't automatically mean early explosion. Early explosion (detonation) happens because the CR is too high for the octane gas being run. Lower octane gas has a faster burn rate therefore is more susceptible to detonation. Compressing the AF mixture creates heat. Heat can set off lower octane gas sooner than it can higher octane gas. Very high CR as in 13+ to one would definately mean early explosion if run on street octane. That's where the misinterpretation came in. For the requirements of a 10:1 or so CR mini-me, premium octane pump gas would be sufficient.

if you dont swap your ECU with the head (and mess with the wiring) then you will have to rig up a Vtec control switch, which still works, but it wont be as effective, since the ECU vtec control also changes the fuel curve if im not mistaken.

Correct.

In fact, if you don't change your ECU to a vtec one, a mini-me swap is pointless and will actually run slower than a stock A6. The a6 cam was designed without vtec in mind which means there's only one cam profile. This profile is designed to work well throughout the entire rpm band. If you slap a vtec head onto an a6 block and don't change the ECU, what you get is an engine that is always stuck on the low profile cam. This means it'll choke at high RPMs because the engine never switches over to the high profile cam lobes.

 

[downest]

Aren't there other ways to make the cam profile change, like RPM switches and such?

 

[dohcrxl]

Yes, but if you are not using a vtec ecu it's still not as good as if you were. Employing an rpm switch will get the pins to slide engaging the high profile cam lobes but the fuel curve from the non-vtec ecu still cannot accomodate the extra added air now being introduced into the engine.

As in the example of slapping on a vtec head and not being able to engage vtec, you're choking because there's not enough air due to the head being stuck on the low lift cam lobes. In this case where you are engaging vtec with an rpm switch but no vtec ecu, you're choking because there's not enough fuel being sent by the ecu.